North Atlantic right whale in the context of "R-selected species"

The r/K selection theory is an evolutionary hypothesis examining the selection of traits in an organism that trade off between quantity and quality of offspring. Species which produce more offspring at the expense of reduced individual parental investment are termed r-strategists, while those which make greater parental investment at the expense of a reduced quantity of offspring are termed K-strategists. The occurrence of the two varies widely, seemingly to promote success in particular environments.

The concepts of quantity or quality offspring are sometimes referred to in ecology as "cheap" or "expensive", a comment on the expendable nature of the offspring and parental commitment made. The stability of the environment can predict if many expendable offspring are made or if fewer offspring of higher quality would lead to higher reproductive success. An unstable environment would encourage the parent to make many offspring, because the likelihood of all (or the majority) of them surviving to adulthood is slim. In contrast, more stable environments allow parents to confidently invest in one offspring because they are more likely to survive to adulthood.

Right whales are three species of large baleen whales of the genus Eubalaena: the North Atlantic right whale (E. glacialis), the North Pacific right whale (E. japonica) and the southern right whale (E. australis). They are classified in the family Balaenidae with the bowhead whale. Right whales have rotund bodies with arching rostrums, V-shaped blowholes and dark gray or black skin. The most distinguishing feature of a right whale is the rough patches of skin on its head, which appear white due to parasitism by whale lice. Right whales are typically 13–17 m (43–56 ft) long and weigh up to 100 short tons (91 t; 89 long tons) or more.

All three species are migratory, moving seasonally to feed or give birth. The warm equatorial waters form a barrier that isolates the northern and southern species from one another although the southern species, at least, has been known to cross the equator. In the Northern Hemisphere, right whales tend to avoid open waters and stay close to peninsulas and bays and on continental shelves, as these areas offer greater shelter and an abundance of their preferred foods. In the Southern Hemisphere, right whales feed far offshore in summer, but a large portion of the population occur in near-shore waters in winter. Right whales feed mainly on copepods but also consume krill and pteropods. They may forage the surface, underwater or even the ocean bottom. During courtship, males gather into large groups to compete for a single female, suggesting that sperm competition is an important factor in mating behavior. Gestation tends to last a year, and calves are weaned at eight months old.